Gary McSheffrey gaves Blues the perfect start when he netted from the penalty spot just 3 minutes into the game at St Andrews after Cameron Jerome had been brought down in the box by David Gray.
Rodrigo Possebon equalised for Ole Gunnar Solskjaer's side 12 minutes later but Jerome, on his return from injury, put Blues 2-1 ahead just 8 minutes before the half time interval.
Jerome gave Blues a two goal cushion twelve minutes after the restart when he netted his second and Blues' third goal.
United's youngster's were not done for however and they reduced the deficit to 3-2 on 70 minutes when Gray atoned for giving away the first half penalty.
Evandro Brandao earned a draw for the visitors when he netted just five minutes from time.